MAP type QFN semiconductor packages consist of multiple units arranged in an array format. Multiple units are manufactured on one substrate bar and are then divided into single units by sawing through the bar. The bar has the function of facilitating the process of bonding the wires from the die to the package terminals, which is more easily carried out if the package units are supported on a single substrate.
FIG. 1 illustrates the typical construction of QFN semi conductor package. The package comprises a semi conductor die 302 supported on a die attachment pad 201 and connected through wires 202 to interconnection pads 200. The whole assembly is encapsulated in an encapsulation material 300, typically a polymer. Such packages are then placed on motherboards to form part of an electronic circuit.
The process for producing a typical package is illustrated in FIGS. 2a) to 2g) and is carried out by first attaching an etched leadframe onto backing tape (FIG. 2a). FIG. 2b) illustrates that the semiconductor die is next attached onto the die attachment pads on the leadframe. Electric connection is then created between the semiconductor die and interconnection pads by bonding wirebonds, such as gold wirebonds, between the semiconductor die and interconnection pads. FIG. 2d) shows that the assembly is then encapsulated to form a package. The backing tape prevents mould bleed of the filler material.
After the encapsulation material has cured the backing tape is removed. This is illustrated in FIG. 2e). The panel is then mounted on a tape or chuck and sawn with a saw blade to divide the panel into discrete package units. The saw is required to cut through two materials, namely the leadframe material and the encapsulation material. FIG. 2g) illustrates the final product of semi conductor packages in single units.
Tie bars are also used to hold the units together in a single panel.
These known methods for manufacturing semiconductor packages have problems with limited design flexibility with respect to leadframe positioning and limitations on reducing the size of the package. Semiconductor packages made from this method are also often not sufficiently robust to withstand certain end uses.
A semiconductor package, and a method for making the same, is required that is more flexible in design with respect to the location of the contact pads and die attachment pads and also in terms of the size and weight of the package.